Prior methods do not permit real-time in situ detection and analysis of the various gas species present in a heat treating furnace. This inability to detect and analyze results in an inability to precisely control, resulting in waste of energy and materials and needless pollution. A variety of prior art techniques take off a slip stream of the gas for analysis. Such slip stream analyses require that the gas sample be cooled, possibly resulting in changes in the gas composition. Further, the time inherently involved in isolating and cooling the gas sample results in a time lag, which prevents real time in-situ analysis.